This invention relates to a hydraulic-oil feeding device for a hydraulically operated injection timing mechanism disposed on the injection pump shaft of an injection pump. This arrangement controls the injection start for multicylinder air-compressing injection-type internal combustion engines.
In conventional hydraulically operated injection timing mechanisms, the effective working surface of an adjusting element is arranged in the injection timing mechanism rotating at pump speed. In this case, the feeding of the hydraulic medium takes place according to U.S. Pat. No. 3,401,572 via a duct and a ring groove on the housing and cross bores and longitudinal bores in the injection pump shaft.
It is known that the drive torque of the injection pump takes an extremely irregular course. The required peak torque during the actual injection phases is several times that of the mean drive torque. The injection timing mechanism must transfer these peak torques completely. Therefore, in the case of hydraulically operated injection timing mechanisms, i.e., those with electric control, the effective working surfaces and operating pressures must be designed for the torque peaks.
An object of the invention is to provide a structurally simple hydraulic-oil feeding device without additional control elements by means of which the transfer of the torque peaks, with respect to function, can be separated from the actual adjusting.
These objects are achieved by providing a hydraulic oil feeding device which has a pump shaft partially disposed in an injection pump housing. A pump feeding member is also provided in the pump housing. A passage forming means is provided between the pump feeding member and the pump shaft.
During each injection process the connection at the transition from the hydraulic-oil feeding member in the injection pump housing to the passage arrangement in the injection pump shaft is interrupted over a certain angle-of-rotation area. Therefore, no hydraulic medium can flow in or out at the injection timing mechanism during the injection process. The passage is open in between injection processes. The two functions of the injection timing mechanism, namely the transfer of the pump drive torques and the adjusting function, are therefore disconnected. In the case of injection timing mechanisms of this type, the effective surfaces and the operating pressures must therefore no longer be designed for the high torque peaks.
The design according to the invention does not require any additional components for the disconnecting. The only measure that is required is a different manufacturing process at the injection pump shaft or at the injection pump housing. The disconnecting can therefore take place independently in a speed-synchronized and phase-synchronized manner without any control from the outside.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.